Air filters for capturing dust, particulate matter, and other airborne materials such as animal hair and dander are available in varieties of prescribed rectangular sizes that are typically incremented by inches along each of two sides. Each typical home or business HVAC air-handling system requires periodic or occasional replacement of a particularly dimensioned filter, and consumers are thus burdened with finding an appropriately sized replacement. In reality, the receptacle structures of the air-handling systems are ultimately not precisely dimensioned according to even their nominal dimensions, and so even when an appropriately labeled filter is found, a perfect fit, with well-sealed edges, without any deformation of the replacement filter is ultimately not assured.
Compromises are thus made, including for example the use of filters that are bit small or large in one or both rectangular dimensions, and frustrated consumers even delay or neglect suggested periodic filter replacement. When air driven through an air-handling system bypasses an improperly fitted filter, airborne matter is not optimally trapped at the filter, which can permit the accumulation of matter on HVAC system components and cause or aggravate respiratory problems. When filter replacement schedules are missed, filter blockage by matter accumulated in an old filter can increase system power consumption and wear, and can harbor microbial growth, which also can also adversely affect respiratory health.